It takes a lot of energy to warm up water. However, the oceans do absorb heat, and they do get warmer. This warmer water causes sea ice to begin to melt in the Arctic.

Information from NASA's Earth satellites shows us that every summer, some Arctic ice melts and shrinks, getting smallest by September. Then, when winter comes, the ice grows again. But since 1979, the September ice has been getting smaller and smaller and thinner and thinner. So, just a small amount of warming can have a huge effect over several years.

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